The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to produce drivers for the switching transistors utilized in non-linear power supply controllers. In one particular type of controller, commonly referred to as a synchronous buck controller, two drivers were utilized to drive to power transistors. One power transistor was connected to switch a voltage to supply current to an inductor. The second transistor, often referred to as a synchronous rectifier, was connected to discharge the inductor. Both transistors typically were controlled by a pulse width modulated (PWM) power supply controller. One example of such a driver is known as the ADP3410 produced by Analog Devices of Norwood Mass. Under some conditions, the PWM controller would shutdown and stop providing PWM pulses to the drivers. When this occurred, the inductor would discharge through the synchronous rectifier transistor which would result in ringing that eventually caused the output voltage to be pulled below the ground potential of the system. Pulling the output voltage below ground often resulted in damage to the electronic components connected to the output of the power supply controller.
Accordingly, it is desirable to have a transistor driver that reduces ringing on the output when the PWM controller shuts down.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention.